Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits

ABSTRACT

Acid copper electroplating baths provide improved low internal stress copper deposits with good ductility. The acid copper electroplating baths include one or more polyallylamines and certain sulfur containing accelerators. The acid copper electroplating baths may be used to electroplate thin films on relatively thin substrates to provide thin film copper deposits having low internal stress and high ductility.

FIELD OF THE INVENTION

The present invention is directed to a copper electroplating bath forelectroplating low internal stress copper deposits having goodductility. More specifically, the present invention is directed to acopper electroplating bath for electroplating low internal stress copperdeposits having good ductility where the acid copper electroplating bathincludes polyallylamine in combination with certain sulfur containingaccelerators.

BACKGROUND OF THE INVENTION

Internal or intrinsic stress of electrodeposited metals is a well knownphenomenon caused by imperfections in the electroplated crystalstructure. After the electroplating operation such imperfections seek toself correct and this induces a force on the deposit to contract(tensile strength) or expand (compressive stress). This stress and itsrelief can be problematic. For example, when electroplating ispredominantly on one side of a substrate it can lead to curling, bowingand warping of the substrate depending on the flexibility of thesubstrate and the magnitude of the stress. Stress can lead to pooradhesion of the deposit to the substrate resulting in blistering,peeling or cracking. This is especially the case for difficult to adheresubstrates, such as semiconductor wafers or those with relatively smoothsurface topography. In general, the magnitude of stress is proportionalto deposit thickness thus it can be problematic where thicker depositsare required or indeed may limit the achievable deposit thickness.

Most metals including copper deposited from an acid electroplatingprocess exhibits internal stress. Commercial copper acid electroplatingprocesses utilize various organic additives which beneficially modifythe electroplating process and deposit characteristics. It is also knownthat deposits from such electroplating baths may undergo roomtemperature self annealing. Transformation of the grain structure duringsuch self annealing concurrently results in a change in the depositstress, often increasing it. Not only is internal stress problematic initself but is typically subject to change on aging as the deposit selfanneals with time resulting in unpredictability.

The fundamental mechanism of alleviating intrinsic stress in copperelectroplating is not well understood. Parameters, such as reducingdeposit thickness, lowering current density, i.e., plating speed,substrate type, seed layer or under plate selection, electroplating bathcomposition, such as anion type, additives, impurities and contaminantsare known to affect deposit stress. Such empirical means of reducingstress have been employed though typically are not consistent orcompromise the efficiency of the electroplating process.

Another important parameter of copper deposits is their ductility.Ductility may be defined as a solid materials ability to deform undertensile stress. Copper deposits with high ductility are desired toprevent or reduce the potential for the copper to crack under tensilestress over time. Ideally, a copper deposit has a relatively lowinternal stress and a high ductility; however, there is typically atradeoff between internal stress and ductility. Accordingly, there isstill a need for a copper electroplating bath and method whichalleviates internal stress in copper deposits as well as providing goodor high ductility.

SUMMARY OF THE INVENTION

An acid copper electroplating bath includes one or more sources ofcopper ions, one or more electrolytes, one or more polyallylamines, oneor more of (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acidsthereof and salts thereof, and one or more suppressors.

Methods include contacting a substrate with an acid copperelectroplating bath comprising one or more sources of copper ions, oneor more electrolytes, one or more polyallylamines, one or more of(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acids thereof andsalts thereof, and one or more suppressors; and electroplating lowinternal stress and high ductility copper on the substrate.

The present invention is also directed to a copper film having aninitial internal stress from 0 psi to 950 psi and an internal stressafter ageing from 300 psi to 900 psi and an elongation of 8% or greaterat loads of maximum tensile stress of 50 lbf or greater.

The acid copper deposits are of low internal stress with relativelylarge grain structure. The internal stress and grain structure do notsubstantially change as the deposit ages, thus increasing predictabilityof the performance of the copper electroplating bath and the depositplated therefrom. The low internal stress copper deposits have good orhigh ductility as well such that the copper deposits do not readilycrack on substrates in contrast to many conventional copper deposits.The copper electroplated from the baths of the present invention have agood balance between low internal stress and ductility not found whenelectroplating copper from many conventional copper baths. The copperelectroplating baths may be used to deposit copper films on relativelythin substrates without substantial concern that the thin substrates maybow, curl, warp, blister, peel or crack.

DETAILED DESCRIPTION OF THE INVENTION

The following abbreviations have the following meanings unless thecontext clearly indicates otherwise: ° C.=degrees Celsius; g=grams;mL=milliliter; L=liter; ppm=parts per million=mg/L; A=amperes=Amps;DC=direct current; dm=decimeter; mm=millimeter; μm=micrometers;nm=nanometers; Mw=weight average molecular weight in g/mole;SEM=scanning electron micrograph; ASD=A/dm²; 2.54 cm=1 inch;lbf=pound-force=4.44822162 N; N=newtons; psi=pounds per squareinch=0.06805 atmospheres; 1 atmosphere=1.01325×10⁶ dynes/squarecentimeter; and RFID=radio frequency identification.

As used throughout this specification, the terms “depositing”, “plating”and “electroplating” are used interchangeably. The term “moiety” means apart or a functional group of a molecule. The moiety “

” —CH₂—CH₂—. Indefinite articles “a” and “an” include both the singularand the plural. The term “ductility” means a solid material's ability todeform under tensile stress. The term “tensile stress” means the maximumstress a material withstands before failing.

All percentages and ratios are by weight unless otherwise indicated. Allranges are inclusive and combinable in any order except where it isclear that such numerical ranges are constrained to add up to 100%.

The copper metal electroplating baths provide thin film copper depositswith a combination of low internal stress and high ductility. Coppermetal is electroplated from low stress and high ductility acid copperbaths which include one or more sources of copper ions, one or moreelectrolytes, one or more polyallylamines, one or more of(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acids thereof or saltsthereof, and one or more suppressors such that the copper deposits havelow internal stress and high ductility, preferably minimal change instress as the copper deposit ages and high ductility. The low internalstress copper deposits may have a matt appearance with a relativelylarge as deposited grain size, typically of 2 microns or more. The acid,low stress, high ductility copper baths also may include one or moresources of chloride ions and one or more conventional additivestypically included in acid copper electroplating baths. Preferably, oneor more sources of chloride ions are included in the acid copperelectroplating baths.

Preferably the one or more polyallylamines have a general formula:

where variable “n” is a number such that the Mw is 1000 g/mole orgreater. Preferably the Mw of the polyallylamines of the presentinvention ranges from 4000 g/mole to 60,000 g/mole, more preferably from10,000 g/mole to 30,000 g/mole.

Polyallylamines are included in the acid copper electroplating baths inamounts of 1 to 10 ppm, preferably from 1 to 5 ppm, more preferably from1 to 2 ppm.

One or more of (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acidsthereof and its alkali metal salts are included in the copperelectroplating baths in amounts of 100 ppm to 300 ppm, preferably from120 ppm to 220 ppm. An acid form of the ester is 1-propanesulfonic acid,3-[(ethoxythioxomethyl)thio]-. The alkali metal salts include(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, potassium salt and(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, sodium salt.Preferably (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, potassiumsalt is included in the copper electroplating baths. While not beingbound by theory, it is believed that the(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester and its alkali metalsalts in combination with the one or more polyallylamines enable thecombination of a low internal stress and high ductility copper metalfilm deposit.

Optionally one or more additional accelerators may be included in thelow stress and high ductility acid copper electroplating baths. Suchaccelerators are preferably compounds which in combination with one ormore suppressors may lead to an increase in plating rate at givenplating potentials. Such optional accelerators are 3-mercapto-1-propanesulfonic acid, ethylenedithiodipropyl sulfonic acid,bis-(ω-sulfobutyl)-disulfide, methyl-(w-sulfopropyl)-disulfide,N,N-dimethyldithiocarbamic acid (3-sulfopropyl) ester,3-[(amino-iminomethyl)-thiol]-1-propanesulfonic acid,3-(2-benzylthiazolylthio)-1-propanesulfonic acid,bis-(sulfopropyl)-disulfide and alkali metal salts thereof. Preferably,such accelerators are excluded from the copper electroplating baths.

When the optional accelerators are included, they are included inamounts of 1 ppm and greater. Typically such accelerators may beincluded in the acid copper electroplating baths in amounts of 2 ppm to500 ppm, more typically from 2 ppm to 250 ppm.

Suppressors included in the low stress, high ductility acid copperelectroplating baths include, but are not limited to, polyoxyalkyleneglycols, carboxymethylcellulose, nonylphenolpolyglycol ether,octandiolbis-(polyalkylene glycolether), octanolpolyalkylene glycolethers, oleic acidpolyglycol ester, polyethylenepropylene glycol,polyethylene glycol, polyethylene glycoldimethylether, polyoxypropyleneglycol, polypropylene glycol, polyvinylalcohol, stearic acid polyglycolester and stearyl alcohol polyglycol ether. Such suppressors areincluded in amounts of 0.1 g/L to 10 g/L, preferably from 0.1 g/L to 5g/L, more preferably from 0.1 g/L to 2 g/L and most preferably from 0.1g/L to 1 g/L.

Suitable copper ion sources are copper salts and include withoutlimitation: copper sulfate; copper halides such as copper chloride;copper acetate; copper nitrate; copper tetrafluoroborate; copperalkylsulfonates; copper aryl sulfonates; copper sulfamate; copperperchlorate and copper gluconate. Exemplary copper alkane sulfonatesinclude copper (C₁-C₆)alkane sulfonate and more preferably copper(C₁-C₃)alkane sulfonate. Preferred copper alkane sulfonates are coppermethanesulfonate, copper ethanesulfonate and copper propanesulfonate.Exemplary copper arylsulfonates include, without limitation, copperbenzenesulfonate and copper p-toluenesulfonate. Mixtures of copper ionsources may be used. One or more salts of metal ions other than copperions may be added to the acid copper electroplating baths. Typically,the copper salt is present in an amount sufficient to provide an amountof copper ions of 10 to 400 g/L of plating solution. The electroplatingbaths do not include any alloying metals. The electroplating baths aredirected to thin film copper deposits, not copper alloy deposits or anyother metal or metal alloy.

Suitable electrolytes include, but are not limited to, sulfuric acid,acetic acid, fluoroboric acid, alkanesulfonic acids such asmethanesulfonic acid, ethanesulfonic acid, propanesulfonic acid andtrifluoromethane sulfonic acid, aryl sulfonic acids such asbenzenesulfonic acid, p-toluenesulfonic acid, sulfamic acid,hydrochloric acid, hydrobromic acid, perchloric acid, nitric acid,chromic acid and phosphoric acid. Mixtures of acids may be used in thepresent metal plating baths. Preferred acids include sulfuric acid,methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,hydrochloric acid and mixtures thereof. The acids may be present in anamount in the range of 1 to 400 g/L. Electrolytes are generallycommercially available from a variety of sources and may be used withoutfurther purification.

One or more optional additives may also be included in theelectroplating composition. Such additives include, but are not limitedto, levelers, surfactants, buffering agents, pH adjustors, sources ofhalide ions, organic acids, chelating agents and complexing agents. Suchadditives are well known in the art and may be used in conventionalamounts.

Levelers may be included in the acid copper electroplating bath. Suchlevelers include, but are not limited to, organic sulfo sulfonates suchas 1-(2-hydroxyethyl)-2-imidazolidinethione (HIT), 4-mercaptopyridine,2-mercaptothiazoline, ethylene thiourea, thiourea, those disclosed inU.S. Pat. No. 6,610,192 to Step et al., U.S. Pat. No. 7,128,822 to Wanget al., U.S. Pat. No. 7,374,652 to Hayashi et al. and U.S. Pat. No.6,800,188 to Hagiwara et al. Such levelers may be included inconventional amounts. When they are included, the may be included inamounts of 1 ppb to 1 g/L. Preferably the levelers are excluded from thebaths.

Conventional nonionic, anionic, cationic and amphoteric surfactants maybe included in the acid copper electroplating baths. Such surfactantsare well known in the art and many are commercially available. Typicallythe surfactants are nonionic. In general, surfactants are included inconventional amounts. Typically they may be included in theelectroplating baths in amounts of 0.05 g/l to 15 g/L.

Halogen ions include chloride, fluoride, and bromide. Such halides aretypically added into the bath as a water soluble salt or acid.Preferably, the copper electroplating baths include chloride. Chlorideis preferably introduced into the bath as hydrochloric acid or as sodiumchloride or potassium chloride. Preferably chloride is added to the bathas hydrochloric acid. Halogens may be included in the baths in amountsof 20 ppm to 500 ppm, preferably 20 ppm to 100 ppm.

The low stress, high ductility acid copper electroplating baths have apH range less than 1 to less than 7, preferably from less than 1 to 5,more preferably from less than 1 to 2, most preferably the pH is lessthan 1 to 1.

Electroplating may be by DC plating, pulse plating, pulse reverseplating, light induced plating (LIP) or light assisted plating.Preferably the low stress, high ductility copper films are plated by DC,LIP or light assisted plating. In general, current density ranges from0.5-50 ASD depending on the application. Typically, the current densityranges from 1-20 ASD or such as from 4-20 ASD or 15-20 ASD.Electroplating is done at temperature ranges from 15° C. to 80° C. orsuch as from room temperature to 60° C. or such as from 20° C. to 40° C.or such as from 20° C. to 25° C.

The internal stress and ductility of the copper films may be determinedusing conventional methods. Typically low internal stress is measuredusing a deposit stress analyzer, such as is available from SpecialtyTesting and Development Co., Jacobus, Pa. The low internal stress may bedetermined by the equation S=U/3TxK, where S is stress in psi, U isnumber of increments of deflection on a calibrated scale, T is depositthickness in inches and K is the test strip calibration constant. Theconstant may vary and is provided with the deposit stress analyzer. Lowinternal stress is measured immediately after plating and then afterageing for a few days, preferably two days after the copper film isdeposited on a substrate, such as a conventional copper/beryllium alloytest strip. Internal stress measurements immediately afterelectroplating and after ageing are made at room temperature. While roomtemperature may vary, for purposes of measuring internal stress, roomtemperature typically ranges from 18° C. to 25° C., preferably from 20°C. to 25° C. Preferably, a copper film of 1-10 μm is plated on the teststrip, more preferably 1-5 μm. Initial internal stress which is measuredimmediately after plating copper on the substrate may range from 0 psito 950 psi, preferably from 0 psi to 900 psi, more preferably from 0 psito 850 psi at room temperature. After ageing, such as for two days, theinternal stress may range from 300 psi to 900 psi, preferably from 300psi to 850 psi, more preferably from 300 psi to 840 psi at roomtemperature. While internal stress may vary slightly from the two daysageing time period, the measurement of the internal stress of a copperfilm of the present invention typically does not significantly change atroom temperature after the two day ageing period.

Ductility is measured using conventional elongation tests and apparatus.Preferably, elongation testing is done using industrial standardIPC-TM-650 methods with an apparatus such as an Instron pull tester33R4464. Copper is electroplated on a substrate such as a stainlesssteel panel. Typically copper is electroplated as a thin film on thesubstrate to a thickness of 50-100 μm, preferably from 60-80 μm. Thecopper is peeled from the substrate and annealed for 1-5 hours,preferably from 2-5 hours. Annealing is done at temperatures of 100-150°C., preferably from 110-130° C., and then the copper is allowed to cometo room temperature. Elongation or load of maximum tensile stress istypically not a pre-set parameter. The greater the load of maximumtensile stress a material can withstand before failing or cracking, thehigher or the better the ductility. Typically elongation is done atloads of maximum tensile stress of 50 lbf or greater. Preferably,elongation is done at 60 lbf or greater. More preferably elongation isdone at loads of maximum tensile stress of 70 lbf to 90 lbf. Elongationranges from greater than or equal to 8%, preferably from 9% to 15%.

The low stress, high ductility acid copper electroplating baths andmethods are used to plate copper on relatively thin substrates such assemiconductor wafers of 100-220 μm or such as from 100-150 μm, or onsides of substrates where bowing, curling or warping are problems. Thelow stress, high ductility acid copper electroplating baths may also beused to plate copper on difficult to adhere to substrates whereblistering, peeling or cracking of the deposit are common. For example,the methods may be used in the manufacture of printed circuit and wiringboards, such as flexible circuit boards, flexible circuit antennas, RFIDtags, electrolytic foil, semiconductor wafers for photovoltaic devicesand solar cells, including interdigitated rear contact solar cells,heterojunction with intrinsic thin layer (HIT) cells and fully platedfront contact cells. The acid copper electroplating baths are used topreferably plate copper at thickness ranges of 1 μm to 5 mm, morepreferably from 5 μm to 1 mm. When copper is used as the principleconductor in the formation of contacts for solar cells, the copper ispreferably plated to thickness ranges of 1 μm to 60 μm, more preferablyfrom 5 μm to 50 μm.

The copper deposits are of low internal stress with relatively largegrain structure. In addition, the internal stress and grain structure donot substantially change as the deposit ages, thus increasingpredictability of the performance of the copper electroplating bath andthe deposit plated therefrom. The low internal stress copper depositshave good ductility as well such that they do not readily crack onsubstrates in contrast to many conventional copper deposits. The copperelectroplated from the baths of the present invention have a goodbalance between low internal stress and ductility not found whenelectroplating copper from many conventional copper baths. The copperelectroplating baths may be used to deposit copper on relatively thinsubstrates without substantial concern that the substrate may bow, curl,warp, blister, peel or crack.

The following examples are provided to illustrate the invention, but arenot intended to limit its scope.

EXAMPLE 1

The following aqueous acid copper electroplating baths were prepared.

TABLE Component Bath 1 Bath 2 Bath 3 Bath 4 Copper sulfate 160 g/L 160g/L 160 g/L 160 g/L Sulfuric acid 150 g/L 150 g/L 150 g/L 150 g/LChloride (as 60 ppm 60 ppm 60 ppm 60 ppm hydrochloric acid) Bis-sodium 04 ppm 4 ppm 4 ppm sulfopropyl- disulfide 3-mercapto-1- 0 6 ppm 0 6 ppmpropane sulfonic acid, sodium salt (O- 175 ppm 0 0 0 Ethydithio-carbonato)- S-(3-sulfopropyl)- ester, potassium salt Polyoxy-alkylene0.15 g/L 0.15 g/L 0.15 g/L 0.15 g/L glycol (PolyMax ™ PA-66/LC solution)Polyethylene 0.18 g/L 0.18 g/L 0.18 g/L 0.18 g/L glycol (PEG 12000)Polyallylamine 1.25 ppm 0 0 0 (Mw = 15000) Linear 0 0 0 0.75 ppmpolyethyleneimine (Mw = 2000)

The components of the copper electroplating baths were made up usingconventional laboratory procedures where organics were added to waterfollowed by adding the inorganic components. Stirring or agitation withheat application at temperatures of below 30° C. was done to be certainthat all of the components were solubilized in the water. The baths wereallowed to come to room temperature prior to copper electroplating. ThepH of the acid copper electroplating baths ranged from less than 1 to 1at room temperature and during copper electroplating.

EXAMPLE 2

Two flexible copper alloy foil test strips were coated on one side witha dielectric to enable single sided plating on the uncoated side. Thetest strips were taped to a support substrate with platers tape andplaced in a haring cell containing an acid copper plating bath havingthe formulation of Bath 1 of the table in Example 1. The bath wasmaintained at room temperature. A copper metal strip was used as ananode. The test foil strips and anode were connected to a rectifier. Thetest foil strips were copper plated at an average current density of 2ASD to deposit a thickness of 5 μm of copper on the uncoated side ofeach strip. After plating was completed the test strips were removedfrom the haring cell, rinsed with wafer, dried and the platers tape wasremoved from the test strips. The internal stress of the copper depositon the strips was determined to be 838 psi. The stress was determinedusing the equation S=U/3TxK, where S is stress in psi, U is number ofincrements of deflection on the calibrated scale. T is deposit thicknessin inches and K is the test strip calibration constant. After the teststrips aged for 2 days, the stress for each strip was determined to be837 psi. The internal stress remained substantially the same for thecopper deposits after ageing.

An elongation test was also performed using industrial standardIPC-TM-650 methods. 75 μm of copper was plated on stainless steel panelat 3.8 ASD. The copper film was peeled off after plating and annealedfor 4 hours at 125° C. The pull test was done on an Instron pull tester33R4464. Elongation for Bath 1 was 14%, and load at maximum tensilestress was 76 lbf. The results showed that the internal stress was lowand the ductility was high for the copper deposit electroplated from thebath containing polyallylamine and(O-ethydithiocarbonato)-S-(3-sulfopropyl)-ester, potassium salt.

EXAMPLE 3 Comparative

Two flexible copper/beryllium alloy foil test strips were coated on oneside with a dielectric to enable single sided plating on the uncoatedside. The test strips were taped to a support substrate with platerstape and placed in a haring cell containing acid copper plating Bath 2.The bath was at room temperature. A copper metal strip was used as ananode. The test foil strips and anode were connected to a rectifier. Thetest foil strips were copper plated at an average current density of 2ASD to deposit a copper thickness of five μm on the uncoated side ofeach strip. After plating was completed the test strips were removedfrom the haring cell, rinsed with wafer, dried and the platers tape wasremoved from the test strips. The test strips were inserted at one endinto screw clamps of the deposit stress analyzer. The internal stress ofthe copper deposit on the strips was determined to be 211 psi. Thestress was determined using the equation S=U/3TxK, where S is stress inpsi, U is number of increments of deflection on the calibrated scale, Tis deposit thickness in inches and K is the test strip calibrationconstant. After the test strips aged for 2 days, the stress for eachstrip was determined to be 299 psi.

An elongation test was also performed using industrial standardIPC-TM-650 methods. 75 μm copper was plated on a stainless steel panelat 3.8 ASD. The copper film was peeled off after plating and annealedfor 4 hours at 125° C. The pull test was done on the Instron pull tester33R4464. Elongation for the copper plated from Bath 2 was 7%, and loadat maximum tensile stress was only 50 lbf. Although the internal stresswas low, the ductility of the copper was not as high as in Bath 1 whichincluded the polyallylamine. Bath 2 was an example of a conventionalacid copper electroplating bath which typically electroplates copperfilm where internal stress is low; however, ductility is undesirablylow.

EXAMPLE 4 Comparative

Two flexible copper/beryllium alloy foil test strips were coated on oneside with a dielectric to enable single sided plating on the uncoatedside. The test strips were taped to a support substrate with platerstape and placed in a haring cell containing acid copper plating Bath 3in the table of Example 1. The bath was at room temperature. A coppermetal strip was used as an anode. The test foil strips and anode wereconnected to a rectifier. The test foil strips were copper plated at anaverage current density of 2 ASD to deposit copper at a thickness of 5μm on the uncoated side of each strip. After plating was completed thetest strips were removed from the haring cell, rinsed with wafer, driedand the platers tape was removed from the test strips. The test stripswere inserted at one end into screw clamps of the deposit stressanalyzer. The internal stress of the copper deposit on the strips wasdetermined to be 1156 psi. The stress was determined using the equationS=U/3TxK, where S is stress in psi, U is number of increments ofdeflection on the calibrated scale, T is deposit thickness in inches andK is the test strip calibration constant. After test strips aged for 2days, the stress for each strip was determined to be 1734 psi.

An elongation test was also performed using industrial standardIPC-TM-650 methods. 75 μm of copper was plated on a stainless steelpanel at 3.8 ASD. The copper film was peeled off after plating andannealed for 4 hours at 125° C. The pull test was done on the Instronpull tester 33R4464. Elongation for the copper deposit from Bath 3 was16%, and load at maximum tensile stress was 62 lbf. While ductility wasgood for the copper film plated from Bath 3, internal stress exceeded1000 psi which was poor. Bath 3 was another example of a conventionalacid copper electroplating where internal stress is high but ductilityis good.

EXAMPLE 5 Comparative

Two flexible copper/beryllium alloy foil test strips were coated on oneside with a dielectric to enable single sided plating on the uncoatedside. The test strips were taped to a support substrate with platerstape and placed in a haring cell containing acid copper plating bathsimilar to Bath 1 except the branched polyethylenimine was replaced with0.75 ppm of a linear polyethylenimine with a Mw=2000 g/mole and having ageneral formula:

where y is a number such that the weight average molecular weight of thelinear polyethylenimine is around 2000 g/mole.

A copper metal strip was used as an anode. The test foil strips andanode were connected to a rectifier. The test foil strips were copperplated at an average current density of 2 ASD to deposit a copperthickness of five μm on the uncoated side of each strip. After platingwas completed the test strips were removed from the haring cell, rinsedwith wafer, dried and the platers tape was removed from the test strips.The test strips were inserted at one end into screw clamps of thedeposit stress analyzer. The internal stress of the copper deposit onthe strips was determined to be 631 psi. The stress was determined usingthe equation S=U/3TxK, where S is stress in psi, U is number ofincrements of deflection on the calibrated scale, T is deposit thicknessin inches and K is the test strip calibration constant. After the teststrips aged for 2 days, the stress for each strip was determined to be1578 psi.

An elongation test was also performed using industrial standardIPC-TM-650 methods. 75 μm thick copper film was plated on stainlesssteel panel at 3.8 ASD. The copper film was peeled off after plating andannealed for 4 hours at 125° C. The pull test was done on the Instronpull tester 33R4464. Elongation for the copper from the bath was 11.8%,and load at maximum tensile stress was 78 lbf. Although the ductilitywas at a high level, the internal stress exceeded 1000 psi after ageingindicating poor bath performance. The results of Bath 4 with the linearpolyethylenimine were substantially the same as with the copper bathswhich excluded the combination of polyallylamine and(O-ethydithiocarbonato)-S-(3-sulfopropyl)-ester, potassium salt.

What is claimed is:
 1. An acid copper electroplating bath comprising oneor more sources of copper ions, one or more electrolytes, one or morepolyallylamines, one or more of(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acids thereof or itsalkali metal salts and one or more suppressors.
 2. The acid copperelectroplating bath of claim 1, wherein the one or more polyallylamineshave weight average molecular weights of 1000 g/mole or greater.
 3. Theacid copper electroplating bath of claim 1, wherein the one or morepolyallylamines are in amounts of 1 to 10 ppm.
 4. The acid copperelectroplating bath of claim 1, wherein the one or more(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acids thereof or itsalkali metal salts are in amounts of 100 ppm to 300 ppm.
 5. A methodcomprises: a) contacting a substrate with a copper electroplating bathcomprising one or more sources of copper ions, one or more electrolytes,one or more branched polyallylamines, one or more of(O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, acids thereof or itsalkali metal salts and one or more suppressors; and b) electroplatinglow internal stress high ductility copper on the substrate from thecopper electroplating bath.
 6. The method of claim 5, wherein the lowinternal stress high ductility copper has a thickness of 1 μm to 5 mm.7. The method of claim 5, wherein the substrate a flexible circuitboard, flexible circuit antenna, REID tag, electrolytic foil orsemiconductor.
 8. A copper film having an initial internal stress from 0psi to 950 psi and an internal stress after ageing from 300 psi to 900psi and an elongation of 8% or greater at loads of maximum tensilestress of 50 lbf or greater.